The present invention relates to character recognition and, more particularly, to recognition of strings of characters formed with magnetic material in selected geometries on substrates.
Storage of information in one magnetic material based form or another for a subsequent retrieval has become commonplace. In one form, characters with assigned meanings are provided on a nonmagnetic substrate through being formed with magnetizable material thereon in such a manner that they can be recognized both visually and by the resulting characteristic magnetic field distribution patterns they exhibit after magnetization. For example, negotiable bank checks are a common means used in payment processes to provide payment to businesses in exchange for goods and services provided thereby. Such businesses in many situations would like to identify by use of an automatic machine the drawer and the drawer's bank account on which such a check is drawn as means for reviewing any past transactions with the drawer, other's experiences in dealing with the drawer, and account funding. Such information provides a rational basis for determining whether the check in question should be accepted by the business in payment for whatever goods or services are to be provided.
Though such bank checks may vary in size and style, each is typically printed with a series of standardized characters using ink containing magnetizable particles. Such characters then offer the possibility of being recognized automatically by machine after magnetizing these particles thereon through sensing the peculiar magnetic field distributions emanating therefrom due to the particular presences and absences of the magnetizable particles over the area associated with each character.
Over the years, many machine systems have been developed for the purpose of magnetic ink character recognition (MICR) to automate the sensing and identification of such standardized character strings on bank checks. A typical MICR system recognizes the magnetic ink characters on the bank check by passing it by a sensor and deriving a sensor output waveform representing the rates of change of the magnetic fluxes emanating from the character magnetizable particles, as each is peculiarly distributed over the area associated therewith, to distinguish one from another. Because the areal distribution of the magnetic ink associated with each character is unique as formed over a standard 8.times.9 cell matrix containing cells of standard area and form, the waveform derived for each standard character, so defined, after sensing is unique and substantially repeatable.
The accuracy of any particular recognition system turns, first, on the reliability, preservability and accuracy of the printing of the magnetic ink characters on bank checks or other substrates of interest. The accuracy then further depends on the reliability, accuracy and tolerance for degradation and noise in the recognition system in its sensing of changes in the magnetic fluxes of characters moving past the system magnetic field sensor and the subsequent matching of the resulting waveforms with criteria established therein to provide a signal representation for the corresponding character.
Prior art machine recognition systems have addressed the recognition of magnetic ink characters through various methods of converting the waveforms, resulting from detecting the flux changes due to the moving magnetized particles in the ink of a character, to what's desired to be an equivalent digital signal to thereby provide a basis for a recognition process for each character sensed on a bank check. One type of system of this nature, for example, correlates timing pulses with the speed of the movement of the check through the system as found by a mechanically based measurement to represent the timing of magnetic changes indicating the nature and presence of a character. The peak of the signals resulting from such changes must, depending on the polarity thereof, pass beyond corresponding minimum positive and negative thresholds set in the system leading to the pass beyond, and the not pass beyond, results being stored in corresponding positive and negative registers. The outputs of the positive and negative registers are used to ascertain from the waveform character providing it.
Accurate assembling of this peak information for each character based on its magnetic flux change waveform is a problem due to the presence of "noise," i.e. primarily imperfections in the magnetic material of the characters on the bank checks in most circumstances. Imperfections in the magnetic materials due to creases in the paper and bald spots due to misprinting, and to wear in handling, distort the waveform for the affected character. A complex waveform classification scheme such as that just described, employing information as to both positive and negative peaks either passing beyond the corresponding thresholds or not in output waveform from the character sensing, is used by the system to reduce the effect of such noise on the recognition process. This information is matched in the system against characteristic positive and negative peak patterns expected in the waveforms of each character as the basis for several matchings to thereby reduce the likelihood of error in selecting a character to be represented as being like the one providing the waveform.
One problem with such a system is that the limited character quality tolerances of such a scheme can require the setting of the threshold levels for the peaks so that increased accuracy can be obtained only at the expense of an increased rejection rate. Thus, a recognition system that maintains a high degree of accuracy while permitting a relatively high level of noise in the waveforms sensed from passing standardized MICR characters on bank checks or other substrates of interest is desired.